Lempel–Ziv–Welch

Lempel–Ziv–Welch (LZW) is a universal <a href="/facts/Lossless_compression/LS702KsN">lossless compression</a> <a href="/facts/Algorithm/fnl5NmRt">algorithm</a> created by <a href="/facts/Abraham_Lempel/689EaYp3">Abraham Lempel</a>, <a href="/facts/Jacob_Ziv/GKDe7C9b">Jacob Ziv</a>, and <a href="/facts/Terry_Welch/N3yr3mud">Terry Welch</a>. It was published by Welch in 1984 as an improvement to the <a href="/facts/LZ77_and_LZ78/HGH09JM9">LZ78</a> algorithm published by Lempel and Ziv in 1978. Claimed advantages include: simple to implement and the potential for high throughput in a hardware implementation.
A large <a href="/facts/English_language/tpkxGt7b">English</a> <a href="/facts/Text_file/zYW4JmES">text file</a> can typically be compressed via LZW to about half its original size. 
The algorithm became the first widely used universal data compression method used on computers. The algorithm was used in the <a href="/facts/Compress/RLSgGNUX">compress</a> program commonly included in <a href="/facts/Unix/0pNL2seI">Unix</a> systems starting around 1986. It has since disappeared from many distributions, because it both infringed the LZW patent and because <a href="/facts/Gzip/H23uqvyx">gzip</a> produced better compression ratios using the LZ77-based <a href="/facts/DEFLATE/XnBt1GKV">DEFLATE</a> algorithm. The algorithm found wide use when it became part of the <a href="/facts/GIF/HfIBWrIC">GIF</a> image format in 1987. It may optionally be used in <a href="/facts/TIFF/TjBJcLeT">TIFF</a> and <a href="/facts/PDF/C9Mn1vYL">PDF</a> files. Although LZW is available in <a href="/facts/Adobe_Acrobat/M2JSVARa">Adobe Acrobat</a> software, Acrobat by default uses <a href="/facts/DEFLATE/XnBt1GKV">DEFLATE</a> for most text and color-table-based image data in PDF files.

Lempel–Ziv–Welch open-in-new

Lempel–Ziv–Welch